The present invention generally relates to a vehicle molding or trim strip for a vehicle and more particularly, to a process for forming a vehicle molding having an improved cosmetic appearance in the end portions.
Decorative vehicle moldings or trim strips are widely used to enhance the appearance of vehicles such as cars, trucks, vans and the like. Typically, such vehicle moldings are manufactured by a process which includes extrusion of a thermoplastic strip from a single unitary plastic material or multiple plies of different types or colors of plastic materials. Decorative plastic or metallic film may also be applied to the viewing surface of such vehicle moldings. As will be appreciated by those skilled in the art, the extruded plastic material, when cut to a desired length, will have the cut end exposed throughout the cross-section of the molding. In the extrusion operation, it is possible to obtain any one of a wide variety of surface appearances of the vehicle molding as extruded ranging from dull, to matted, to textured or to glossy, depending upon the type of extrusion die and operating conditions. This is well known in the art and does not form a part of the present invention.
However, the surface appearance, as extruded, will usually be different from the surface appearance of an end cut through the cross-section of the molding. The difference in appearance between a surface, as extruded, and a surface of a cut end is magnified in those instances in which a foam plastic strip is extruded since the cellular structure of the foam will be visible on the cut end while the surface as extruded may have a non-cellular or solid structure. Thus, for aesthetic purposes it is not desirable to have an end, which is cut through the cross-section of the extruded length of plastic, exposed to view and much effort has been devoted to providing an end finish to such vehicle moldings which is aesthetically pleasing in appearance. Frequently, it is desired to have the moldings terminate in tapered or pointed ends. However, whether such ends are tapered, pointed or some other configuration, it is indisputably desirable to ensure that no portion of the interior cross-section of the vehicle molding be exposed and that only the decorative surface be exposed when the molding is attached to a vehicle.
Additionally, in many instances the surface appearance of the side of the extruded molding intended to face the vehicle is different from that of the surface intended for viewing. This is particularly true in those moldings having multiple layers with the decorative layer intended for viewing having a different color than the base layer forming the side intended to face the vehicle. In those types of moldings, it is commercially unacceptable for base layers to be visible when the molding is affixed to a vehicle. Finished moldings may be attached to a vehicle by any one of a number of means well-known to those skilled in the art. One such attachment means is a double-faced adhesive foam core strip, one side of which is attached to the vehicle and the other side of which contacts the surface of the molding facing the vehicle (i.e., the surface opposite the decorative viewing surface).
There have been many attempts in the past to provide decorative moldings which have aesthetically pleasing end portions. None of these attempts, however, have materialized into a process in which both the aesthetics as well as the manufacturing costs are advantageous. For example, Cakmakci, U.S. Pat. No. 5,023,033, discloses a method by which a previously extruded length of thermoplastic material intended for viewing is maintained at a cold temperature, well below the softening temperature of the thermoplastic material, during the reshaping operation. A heated mold is moved against surface facing the vehicle of the end portion to be reshaped. Thereafter, the end portion is squeezed between the cold contoured mold face and the heated mold after which it is cooled to set the end portion in conformity with the contoured mold face.
Takeda et al, U.S. Pat. No. 4,489,019, discloses forming a longitudinal molding with non-uniform sections. The process disclosed in Takeda et al begins with an extrusion molded thermoplastic strip which is reshaped to provide a remolded end portion. The extruded thermoplastic strip is placed into a mold, heated and partially fused by high frequency dielectric heating and then, cooled in the mold so that the material is partially remolded. Preferably, the total volume of the whole material placed in the mold is equal to the volume of the cavity of the mold. The heated portions of the longitudinal strips are melted and flow along the surface of the cavity of each of the molds. Takeda et al also disclose reforming the strip around a separately molded clip which may be utilized to connect the part to the vehicle.
Loew, U.S. Pat. No. 3,959,538, discloses contoured end structures for trim strips formed from a length of extruded plastic material. The end structures have various configurations and are produced by removing a portion of the trim strip material as extruded between the side portions thereof to define a pair of V-shaped notches or recesses and then deforming the remaining portions of the trim strip adjacent the recess to close the recess and bring laterally opposite edges thereof into juxtapositional relationship. The juxtaposed edges are then bonded by heat sealing to complete the forming operation.
The method disclosed in Jennings, U.S. Pat. No. 4,174,986, also begins with a length of extruded thermoplastic material such as polyvinylchloride (PVC) which is cut into segments of desired lengths. In accordance with Jennings, an improved method for forming tapered ends is disclosed with the stated purpose of avoiding the tendency of the finished strip to delaminate from the substrate to which it is attached. Jennings discloses a V-shaped wedge cut from an end of the strip, thereby creating two similar triangular legs which are drawn together and adhered to create the pointed taper. The legs at the notched ends are bent upwardly at approximately 45.degree. to counteract the tendency of the end to arch after the taper is formed.
The inventions disclosed in Ives, U.S. Pat. No. 4,617,209, Jackson, U.S. Pat. No. 4,619,847, and Thiel, U.S. Pat. No. 4,719,067 utilize separately molded end caps which are separately adhered or otherwise affixed to the trim strip to provide for the decorative end portion of the finished article. With the exception of Takeda and Cakmakci the above-identified attempts in the art involve costly operations of either cutting and adhering or, separately molding an end cap and adhering or otherwise connecting it to the extruded strip. Additionally, strips formed according to those inventions suffer from an aesthetic standpoint in that the parting line between the connected members is visible on the viewing surface of the finished part unless an additional decorative layer of film is applied thereover which adds to the manufacturing costs.
Similarly, there is no indication in Takeda and Cakmakci that any effort is made to deal specifically with finishing the end portions as proposed in the present invention. Although parts produced according to the invention disclosed in Takeda may not have a parting line on the viewing surface, the method utilized therein results in remelting the entire mass of the strip portion intended to be remolded so that all portions are melted and flow along the surface of the cavity of each of the molds. Such remelting and flowing of the melted surface results in the surface having an appearance different from that of the surface as extruded. Similarly, the method disclosed in Cakmakci requires a subsequent reshaping operation which significantly adds to manufacturing costs and time.
Accordingly, there is a need in the art for a process for forming a molding having an improved cosmetic appearance, especially in the end portions. There is also a need for such a process for forming a vehicle molding which has the combined advantage of improved aesthetics as well as reduced manufacturing costs.